Apparatus and method for detecting splices

ABSTRACT

A spliced conductive fiber is passed through a region in which an electric current is conducted along the fiber. The variations in the current (or voltage) due to the presence of a splice are detected. In one embodiment, the variations are utilized to control a heat source used in fiber processing to prevent rupture of the fiber at the splice as the spliced portions of the fiber pass through the heating zone.

United States Patent [72] lnventors Richard M. Owen [56] References Cited UNITED STATES PATENTS [211 App] NO {$22 Bmw! 2,242,889 5/1941 Keeler 73/160 Filed Begs, 1969 3,037,162 5/1962 Jones et al. 73/159 [45] Patented Apr. 27, 1971 Primary Examiner-Harold Broome [73] Assignee Monsanto Company Assistant Examiner-F. E. Bell St. Louis, Mo. Att0rneys-Vance A. Smith, Russell E. Weinkauf, John D.

Upham and Neal E. Willis [54] AND METHOD FOR DETECTING ABSTRACT: A spliced conductive fiber is passed through a 12C 3D region in which an electric current is conducted along the alms rawmg fiber The variations in the current (or voltage) due to the [52] U.S.Cl 219/505 presence of a splice are detected. In one embodiment, the [51] Int. Cl 05b 1/02 variations are utilized to control a heat source used in fiber [50] Field of Search 73/ 159, processing to prevent rupture of the fiber at the splice as the 160; 219/505 spliced portions of the fiber pass through the heating zone.

14 I0 2 l i ll 20 r 0 l A (p DIGITAL 26 COUNTER 0c POWER SUPPLY I 23 pot/ ER \lg SUPPLY IO 2! II 2 [20 C) \24 T DIGITAL 2 COUNTER Patented April 27, 1971 3,576,425

POWER SUPPLY V I4 l5 IO I II I 20 2/ l L DIGITAL 32 COUNTER .oc POWER &-- I--- /I7 SUPPLY 25 \23 AC 1 r p r 22 TIME 11 To TI 1 T2 T3 RELAY 23 DE-ENERGIZED DE-ENERGIZED DE-ENERGIZED ENERGIZEP CONTACT IS a 25 CLOSED CLOSED CLOSED oP I RELAY 3| DE-ENERGIZED DE-ENERGIZED ENERGIZED DE-ENERGIZEP CONTACT 32 1 CLOSED CLOSED OPEN CLOSED INVENTORS RICHARD M. OWEN JOHN W. BROWN ATTORNEY APPARATUS AND METHOD FOR DETECTING SPLICES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the detection of splices in spliced conductive fibers. More particularly, this invention relates to an apparatus and method for detecting splices in conductive fibers such as graphite fibers. 2. Discussion of Prior Art Problems The many and varied applications of conductive fibrous materials, particularly refractory fibrous materials such as graphite, discovered in recent years has resulted in a tremendous increase in the demand for such fibers. For example, because of their extraordinary high tenacity and modulus together with resistance to high temperatures graphite fibers find wide use as reinforcing elements in advanced materials used in high performance applications, such as rotor blades in jet engines.

Generally, graphite fibers are produced in lengths of a few hundred feet or less. Packaging and certain applications, however, require long or continuous lengths of fiber which are ordinarily wound in good parallel arrangement on drums or spools. It is therefore necessary to adhere the fibers end to end in order to obtain the desired continuous fibers. One manner in which the fibers may be adhered together is by splicing. For example, by overlapping the ends slightly and adhering-the ends with an adhesive substance such as resin, continuous graphite fibers may be fabricated.

In processing spliced graphite fibers, undesired breaks often occur in the fiber at the splice. For example, it is often necessary to heat the fiber to high temperatures. This may be accomplished in a number of ways such as by moving the fibers through a furnace or by passing an electric current of ap propriate magnitude through the fiber so as to heat the fiber by using its electrical resistance. Experience has shown that under heating conditions, the splice often breaks because the adhesive melts or decomposes. A fiber break must necessarily be repaired by resplicing which requires frequent stopping and starting of the fiber process. The resulting time delay, or downtime" is obviously undesirable. Further," the fiber laydown around the drum package may be rendered nonuniform due to the frequent interruption in the fiber collection or takeup. Present techniques utilized to avoid the breaks are generally limited to a visual inspection of the fiber as it approaches the heating region coupled with manually shutting down the heating equipment when a splice is observed. From an economic standpoint, a visual inspection and manual heat control is clearly undesirable. Thus, it would be most advantageous if means were provided for automatically detecting the splices prior to passage thereof through a processing zone such as a heating source together with a simultaneous control of that heat source before entry of the spliced portions of the fiber.

Although the foregoing discussion has been limited to problems in processing spliced graphite fibers, it is pointed out that the prompt detection of spliced portions of any electrically conductive fiber during processing thereof is desirable, particularly when deleterious effects may occur to the spliced portions if processed undetected. Moreover, because commercial demands are often proportional to the quality of fiber, quality control techniques may dictate a need for accurately counting the number of splices in a particular roll of fiber.

Thus, it is a primary object of the present invention to provide an apparatus and method for detecting splices in conductive fibers.

It is another important object of the present invention to provide an apparatus and method for detecting splices in a conductive fiber and, in response thereto, controlling one or more fiber process variables during the processing of the conductive fiber.

BRIEF STATEMENT OF THE INVENTION I It has been observed that when an electric current is passed that the current (or voltage) between the electrodes remains substantially constant until a splice moves therebetween. It has been further noted that the splice generally has a higher resistivity (and therefore lower conductivity) than the fiber. By utilizing the change in current (or voltage) between the electrodes, a processing means such as heating source may be controlled so as to prevent heating the spliced portion to a temperature level which may cause fiber breaks. Other variables such as fiber speed may be controlled equally as well.

Thus, in one embodiment, the present invention avoids the disadvantages stated above by electrically detecting the splices before passage thereof through the processing means.

For purposes of simplicity and clarity, the description herein uses graphite fiber as an example of a conductive fiber. It should be understood, however, that an apparatus and method in accordance with the present invention may be employed to detect splices in any conductive spliced fiber which undergoes a change in electrical characteristics due to the presence of the splices.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, advantages, and variations of the present invention are further detailed in the following description taken in connection with the appended drawings in which:

FIG. 1 is a schematic illustration of one embodiment of the present invention;

FIG. 2 is a schematic illustration of another embodiment of the present invention;

FIG. 3 is a simple timing diagram of the active elements in the embodiment of FIG. 2.

As stated previously, the spliced portion of the graphite fiber does not possess the same electrical characteristics as an unspliced portion. While other varying fiber parameters such as, for example, fiber cross section will cause variations in the fiber electrical characteristics, it has been found that these variations are generally smaller than those caused by splices. Consequently, by utilizing devices which are sensitive to the larger, more pronounced variations, the presence of splices may be detected before the splice portion undergoes graphite processing.

The present invention may be utilized to control any of a plurality of processing means, singularly or in combination. Although the following descriptive matter generally relates to the detection of splices and subsequent control of a heating source, it will be evident from a reading thereof that other processing means may be regulated equally as well. It is more expedient, however, to discuss processing in terms of a single processing means or step in order that the invention may be clearly described.

FIG. I is a simplified schematic diagram showing a means which may be utilized in accordance with the present invention to detect splices and control the heating thereof. A quantity of spliced graphite fiber 10 is wound upon a supply spool 11 and unwinds toward the takeup spool 12. Spool 12 is sur-- face driven by means of the drive roll 27, belt 28 and electric motor 13.

The graphite fiber heating circuit 14, located intermediate the spools 11 and 12 comprises the rolling electrodes 15 and 16 in electrical contact with the fiber 10, an appropriate AC power supply 17, and the normally open contact 18 of the double pole, double throw time delay relay 23.

Positioned intermediate the fiber heating electrode 15 and the supply spool 11 is the splice detection circuit 19 which comprises the rolling electrodes 20 and 21 in electrical contact with the graphite fiber 10, the variable resistor 22, the time delay relay 23, the digital counter 24, the normally closed contact 25 of the time delay relay 23, and an appropriate DC power supply 26. The digital counter 24 and the relay contact 25 are series connected and wired in parallel with the DC power supply 26.

In operation, graphite fiber 10 is continuously forwarded Mun" nInnO'nrnn IE I and m 7.1 In rirmlil Q the time delay relay 23 is energized causing its contact 18 mm closed while contact 25 is open and variable resistor 22 is adjusted to balance the circuit. As the unspliced graphite fiber moves across electrodes 20 and 21, there is no significant variation in the current (or voltage) in circuit 19. Consequently, relay contact 18 remains closed to maintain the heating circuit 14 conductive through the graphite fiber moving across electrodes 1S and 16. The current therein is of sufficient magnitude. to elevate the temperature of the fiber to the desired level.

When a splice passes between electrodes and 21 there is a significant decrease in the fiber conductivity which results in deenergizing the time delay relay 23 and coincident therewith contact 18 is actuated to the open position while contact is actuated to the closed position. With the opening of contact 18, the heating circuit 14 becomes nonconductive with the result that the graphite fiber is no longer maintained at a substantially constant processing temperature.

Due to the time required for the spliced portion to travel from between electrodes 20 and 21 of the detection circuit 19 to a point beyond electrode 16, it is necessary to delay the reenergization of the relay 23 until the splice in the graphite fiber 10 has virtually passed through the furnace 14. This delay may be conveniently accomplished by employing a commercially available variable time-delay relay such as the Type No. CDD-38-30,005, made by the Potter and Brumfield Co. of Princeton, Indiana. By knowing the feed rate of the fiber and the distance residing between the electrodes 20 and 16 the time required for the splice to traverse this distance can be ascertained and set on the variable time-delay relay. Therefore, when a splice moves between electrodes 20 and 21, relay 23 deenergizes and remains in that state until the splice is forwarded to a position immediately past electrode 16. It may be desirable not only to visually indicate the presence of a splice but to maintain an accurate count of the number of splices existing along a given length of the fiber processes. Both may be accomplished simultaneously as illustrated in FIG. 1 wherein the digital counter 24 and the relay contact 25 of detection circuit 19 are wired in parallel with the DC power supply 26. With each deenergization of the relay 23 the contact 25 closes whereupon the counter 24 is cycled one digit to count the splice, thereby indicating and counting the splices.

In the embodiment of FIG. 1, the heating circuit is rendered nonconductive at the moment a spliced fiber region is first detected and becomes conductive again at a predetermined time interval later. The predetermined time interval is substantially equal to the time required by the spliced fiber region to move from the detector through the furnace. Thus, the fiber region which is located between the detector and furnacev at the beginning of the predetermined time interval is not heated by the heating source. For an apparatus having a substantial distance between the detector and furnace, it may be desirable to render the heating circuit nonconductive only during the time interval taken by the spliced fiber region to move by or through the heating source.

A device for accomplishing the above is illustrated by the schematic diagram of FIG. 2 wherein the fiber splice detection circuit comprises the elements of the detection circuit 19 of FIG. 1 in addition to the variable time delay relay 31 having the normally closed contact 32 in the fiber heating circuit 14. The time delay relay 31 and the normally closed relay contact 18 of time delay relay 23 are series connected and parallel wired with counter 24 and DC power supply 26. In operation, circuit 30 is utilized to detect splices in fiber 10. When a splice is detected, relay 23 is deenergized actuating its contacts 18 and 25 to the closed position. Although contact 18 is now closed, time-delay relay 31 is delayed in energizing by the timing means incorporated therein which is preset in accordance with the time required for the detected splice to move from between the electrodes 20 and 21 to a point in close proximity to the electrode 15. As the instant relay 31 times out and becomes energized the contact 32 thereof is actuated to the open position thereby rendering circuit 14 nonconductive.

When the splice moves beyond electrode 16, relay 23 which has remained deenergized throughout the time interval, energizes to actuate the contacts 18 and 25 to the open position whereupon relay 31 is deenergized and its contact 32 is actuated to the closed position to resume the processing of the fiber 10 in the furnace 14. During the time contact 25 was closed the digital counter 24 had cycled through a count of one digit to count the splice having been detected by the circuit 30.

For clarity, FIG. 3 illustrates a timing diagram in which: t is the initial time of splice detection, that is, the time at which a splice moves between electrodes 20 and 21 of circuit 19; t, is the time at which the detected splice moves between electrode 21 of circuit 19 and electrode 15 of circuit 14; t, is the time at which the detected splice moves between electrodes 15 and 16 of circuit 14; and t is the time at which the detected splice moves beyond electrode 16 of circuit 14. It is seen that t t is the time interval taken by a splice to move through circuit 19, t --t, is the time interval taken by the splice to move between circuits 19 and 14, and t t is the time interval required by the splice to move through circuit 14. Thus, it is necessary for relay 23 to delay reenergization for a time period equal to the sum of r -t and 1 -4 i.e., t ',t Relay 32, on the other hand, must delay energization for a time period t l the sum of r,-t and 1 -4,. Both time periodsare easily calculated by using the known fiber speed and distances between the electrodes and circuits.

In summary, breaks in continuous or long lengths of spliced graphite fibers caused by processing the fiber at high temperatures therein are avoided through utilization of the device and method of the present invention. By passing an electric current along the fiber as it moves between and in contact with a pair of spaced electrodes, the change in the current (or voltage) due to a splice may be detected and utilized to render the means for heating the fiber nonoperative during the time interval required for the spliced portion to move by the heating means. Alternatively, the current (or voltage) change may be employed to reduce the temperature level in the heating means, increase the speed of the graphite fiber as the spliced portion passes through the heating means, or alarm an operator as to the presence of a splice.

It should now be apparent that varied techniques of avoiding breaks in the spliced portions of graphite fibers during processing as well as means for counting and visually indicating the presence of splices are available through the teachings as set forth in accordance with the present invention. lt is undetstood that changes made in the present invention that are obvious to those skilled in the art in the light of the foregoing are intended to be within the scope of the present invention as defined by the following claims.

We claim: 1. In a device for processing a spliced graphite fiber including means for moving said fiber from a supply roll to a takeup roll and means for treating said graphite fiber, the improvement which comprises a detecting circuit having spaced electrodes which contact said graphite fiber and a power source for providing an electrical signal along the graphite fiber as it moves between said electrodes; and a sensing means for sensing a variation in the electrical signal due to a splice in the graphite fiber moving between said electrodes; said treating means becoming nonoperative in response to said control means sensing a variation in the electrical signal and remaining nonoperative until the splice moves through said treating means.

2. The device of claim 1 wherein said treating means becomes nonoperative at a first predetermined time interval after said control means senses an electrical signal variation, said first predetermined time period being substantially equal to the time taken by a splice to travel from between said detecting circuit electrodes to said treating means.

3. The device of claim 2 wherein said treating means becomes operative again after a second predetermined time period which follows said first predetermined time period, said second predetennined time period being substantially equal to the time taken by a splice to travel through said treating means.

4. The device of claim 3 wherein said treating means is a heating means comprising an electric circuit having spaced electrodes in contact with said graphite fiber intermediate of said detecting circuit electrodes and said takeup means downstream of said detecting circuit electrodes, at power source for providing an electric current across the graphite fiber between said heating circuit electrodes to heat the graphite fiber, and a contact means, said contact means being operated by said control means and opening said heating cirfcuit after said first predetermined period and closing said heating circuit after said second predetermined time period.

5. The device of claim 4 wherein said control means includes a time delay relay means in said detecting circuit, said time delay relay means becoming deenergized and opening said contact means when the electrical signal across said detecting circuit electrodes varies due to a splice in the graphite fiber and reenergizing and closing said contact means after said second predetermined time period.

6. The device of claim 4 in which said control means includes a time delay relay means in said detecting circuit and a control electric circuit, said control electric circuit including a contact means, a time delay relay means, and a power source wherein said control circuit contact means closes said control circuit in response to the deenergization of said detecting circuit relay means and said heating circuit contact means opens said heating circuit in response to the energization of said control circuit relay means, said control circuit relay means energizing after said first predetermined time period.

7. The device of claim 6 wherein said detecting circuit relay means energizes after said second predetermined time period, said control circuit contact means opening said control circuit in response to said circuit relay means energizing thereby causing said control circuit relay means to deenergize said heating circuit contact means to close said heating circuit.

8. in a method for processing a spliced conductive fiber, the steps of a. continuously moving the conductive fiber from a supply position to a takeup position;

b. continuously passing an electrical signal along the graphite fiber as it moves through a first region intermediate the supply position and takeup position; and

c. detecting the variations in the electrical signal due to the movement of a splice through the first region.

9. The method of claim 8 in which the conductive fiber is a graphite fiber.

10. The method of claim 9 in which the graphite fiber is heated in a second region intermediate the first region and the takeup position, including the additional step of causing the portion of the fiber having the detected splice to move through said first region free of heating by the heating source thereby preventing rupture to occur in the fiber along the spliced portion thereof.

11. The improvement of claim 10 in which the step of heating is accomplished by passing an electric current along said graphite fiber in said first region wherein the current is interrupted after a splice is detected and continued after the splice passes through said first region.

12. The improvement as in claim 11 wherein said current interruption occurs at a first predetermined time interval after a splice is detected and current continuation occurs a second predetermined time interval after said first interval, said first time interval being substantially equal to the time required for a splice to move from the first region to the second region, said second time interval being substantially equal to the time required for a splice to move through the second region. 

1. In a device for processing a spliced graphite fiber including means for moving said fiber from a supply roll to a takeup roll and means for treating said graphite fiber, the improvement which comprises a detecting circuit having spaced electrodes which contact said graphite fiber and a power source for providing an electrical signal along the graphite fiber as it moves between said electrodes; and a sensing means for sensing a variation in the electrical signal due to a splice in the graphite fiber moving between said electrodes; said treating means becoming nonoperative in response to said control means sensing a variation in the electrical signal and remaining nonoperative until the splice moves through said treating means.
 2. The device of claim 1 wherein said treating means becomes nonoperative at a first predetermined time interval after said control means senses an electrical signal variation, said first predetermined time period being substantially equal to the time taken by a splice to travel from between said detecting circuit electrodes to said treating means.
 3. The device of claim 2 wherein said treating means becomes operative again after a second predetermined time period which follows said first predetermined time period, said second predetermined time period being substantially equal to the time taken by a splice to travel through said treating means.
 4. The device of claim 3 wherein said treating means is a heating means comprising an electric circuit having spaced electrodes in contact with said graphite fiber intermediate of said detecting circuit electrodes and said takeup means downstream of said detecting circuit electrodes, a power source for providing an electric current across the graphite fiber between said heating circuit electrodes to heat the graphite fiber, and a contact means, said contact means being operated by said control means and opening said heating circuit after said first predetermined period and closing said heating circuit after said second predetermined time period.
 5. The device of claim 4 wherein said control means includes a time delay relay means in said detecting circuit, said time delay relay means becoming deenergized and opening said contact means when the electrical signal across said detecting circuit electrodes varies due to a splice in the graphite fiber and reenergizing and closing said contact means after said second predetermined time period.
 6. The device of claim 4 in which said control means includes a time delay relay means in said detecting circuit and a control electric circuit, said control electric circuit including a contact means, a time delay relay means, and a power source wherein said control circuit contact means closes said control circuit in response to the deenergization of said detecting circuit relay means and said heating circuit contact means opens said heating circuit in response to the energization of said control circuit relay means, said control circuit relay means energizing after said first predetermined time period.
 7. The device of claim 6 wherein said detecting circuit relay means energizes after said second predetermined time period, said control circuit contact means opening said control circuit in response to said circuit relay means energizing thereby causing said control circuit relay means to deenergize said heating circuit contact meaNs to close said heating circuit.
 8. In a method for processing a spliced conductive fiber, the steps of a. continuously moving the conductive fiber from a supply position to a takeup position; b. continuously passing an electrical signal along the graphite fiber as it moves through a first region intermediate the supply position and takeup position; and c. detecting the variations in the electrical signal due to the movement of a splice through the first region.
 9. The method of claim 8 in which the conductive fiber is a graphite fiber.
 10. The method of claim 9 in which the graphite fiber is heated in a second region intermediate the first region and the takeup position, including the additional step of causing the portion of the fiber having the detected splice to move through said first region free of heating by the heating source thereby preventing rupture to occur in the fiber along the spliced portion thereof.
 11. The improvement of claim 10 in which the step of heating is accomplished by passing an electric current along said graphite fiber in said first region wherein the current is interrupted after a splice is detected and continued after the splice passes through said first region.
 12. The improvement as in claim 11 wherein said current interruption occurs at a first predetermined time interval after a splice is detected and current continuation occurs a second predetermined time interval after said first interval, said first time interval being substantially equal to the time required for a splice to move from the first region to the second region, said second time interval being substantially equal to the time required for a splice to move through the second region. 